A ribbon cassette capable of stabilizing the movement of an ink ribbon.
U.S. Pat. No. 6,290,408 discloses that, with conventional ribbon cassettes, it is difficult to stabilize the ink ribbons during use as printing conditions vary. At column 2 of this patent, and with regard to a conventional ribbon cassette used in thermal printing, it is disclosed that: xe2x80x9cSince the tensile load is applied to the ink ribbon 3 by the agency of the tension shaft of the thermal transfer printer, the tensile load is kept constant for all types of ink ribbons regardless of type. Therefore, all types of ink ribbons are not necessarily able to move steadily. Different types of ink ribbons behave differently when used for printing on the thermal transfer printer. Therefore, printing conditions, such as pressure for pressing the thermal print head against the platen, mode of driving the heating elements of the thermal print head and printing speed are controlled to print images properly. However, it is impossible to stabilize the movement of all types of ink ribbons only through the control of the printing conditions for the thermal transfer printer and, consequently, images are printed in a poor print quality.xe2x80x9d
The solution to this problem that is disclosed and claimed in U.S. Pat. No. 6,290,408 is: xe2x80x9cA ribbon cassette comprising: a take-up reel and a feed reel supported for rotation in a housing, and an ink ribbon wound on the take-up reel and the feed reel; a print head receiving part formed in a section of a passage for the ink ribbon between the take-up reel and the feed reel to receive a thermal print head therein when the ribbon cassette is set in place on a thermal transfer printer; a take-up pinch roller and a feed pinch roller supported for rotation at a position between the print head receiving part and the take-up reel and at a position between the print head receiving part and the feed reel, respectively; and a friction mechanism for exerting a frictional force to the feed pinch roller to apply a tensile load to the ink ribbon, wherein the friction mechanism comprises an elastic friction member capable of exerting a frictional force on a core barrel included in the feed pinch roller by clasping the core barrel.xe2x80x9d
The system described in U.S. Pat. No. 6,290,408 does not allow one to readily vary the tension on the ink ribbon for different conditions. Furthermore, such prior art system does not provide good tension control for used ribbon taken up on the take up spool, which often tends to swell and thus precludes efficient gathering of all of the used ribbon. It is an object of this invention to provide an improved system which overcomes the problems presented by the system of such United States patent.
In accordance with this invention, there is provided a ribbon cassette comprising a supply core, a web disposed on said supply core, a storage core, means for passing said web from said supply core to said storage core, means for increasing the tension on said web as it passes from said supply core to said storage core to produce a tensioned web, a drive roller contiguous with said web, and a nip roller contiguous with said web, wherein said tensioned web is passed in a first rotary direction around a portion of said drive roller, wherein said tensioned web is passed in a second rotary direction opposite to said first rotary direction around a portion of said nip roller, wherein said tensioned web is passed in a in rotary direction identical to said first rotary direction around a portion of said storage core, and wherein said ribbon cassette is comprised of means for compressing said drive roller or said nip roller by at least about 0.001 percent.